#include<bits/stdc++.h>
using namespace std;
int main()
{int n,p=0,k=0;
cin>>n;
if(n%2==0)
{
	p=n/2;
	k=0-p;
}
else if(n%2==1) 
{
	p=(n-1)/2;
	k=n-p;
}
cout<<k;
return 0;
}